Binary Screening
Most of the literature on halftoning discusses techniques that are specifically suited for binary devices. This is to be expected as the earliest halftoning techniques were developed to overcome the limitations in tone rendering of devices that were originally intended for the reproduction of text and line-art only. The most representative example of such a device is the "offset printing press". This device is characterized by a very high spatial resolution--lines with a width of just 20 micron can still consistently be printed--but with essentially only two consistently reproducible tone values corresponding to ink or no ink. Tones of a variable darkness can be rendered on such a device by modulating the size and/or distance between "halftone dots" and this technique is called "halftoning".